A crater in Australia that was carved out by an incoming space rock has been dated to 2.23 billion years old, making the scar the oldest known impact crater on Earth.
Geological activity has obliterated most of the planet’s ancient crust, leaving scientists with little information about Earth’s early history. One of the few remaining chunks of old crust lies in Western Australia, which is where researchers discovered a buried impact crater that they reported in 2003. They suspected that the feature, which they named Yarrabubba crater, could be one of Earth’s oldest impact craters, but could not tell its exact age.
Timmons Erickson at NASA’s Johnson Space Center in Houston, Texas, and his colleagues measured the amounts of uranium and lead in the 70-kilometre-wide crater’s minerals. The results show that Yarrabubba is older than a 2-billion-year-old impact crater in South Africa.
The researchers speculate that if the incoming meteorite hit ice or water, it could have vaporized massive amounts of water. This vapour could have warmed the planet and helped to bring it out of a global deep freeze that drew to a close around that time.